The background description provided is to generally present the context of the disclosure. Work of the inventors, to the extent it may be described in this background section, and aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present technology.
In some automotive applications, low-frequency noise has been a long-standing issue for passenger comfort. Vehicles can generate significant low-frequency noises. These low-frequency noises may emanate from a variety of sources, such as the powertrain and tires of the vehicle, wind noise, and the like.
There are several different solutions for managing low-frequency noises, but many have drawbacks. For example, one solution requires the use of high reflection material. Structures made of high reflection material, such as doors and windows, can reflect noises away from the cabin of the vehicle. However, the reflected noises may cause noise pollution, and the performance of these types of systems is limited by the mass law.
Another solution requires the use of high absorption material. However, conventional porous sound absorbing materials are only efficient for high frequency (greater than 1 kHz) noise reduction due to its high impedance nature. The sound transmission through porous materials is high if the material microstructure has a large porosity.